Expressway following the completion of the highway in the vicinity of the eastern bridge approach. In the mid-1940s, the northern end of US 9 was realigned to enter Canada via Champlain instead of Rouses Point. The old route through Rouses Point became NY 9B. In the mid-1960s, the Adirondack Northway was completed in the vicinity of Champlain, supplanting the northernmost of US 9. US 9 initially overlapped with I-87 from exit 43 to the Canadian border; however, it was truncated to end at exit 43—the last interchange before the border—in the 1970s. Part of US 9's former routing to the border was retained as a service road and was designated as NY 971B, an unsigned reference route. Croton Expressway Since the 1940s, an expressway along the US 9 corridor on the east bank of the Hudson River had been planned. Part of the route later became the New York State Thruway (up to Tarrytown). In 1956, there were plans to continue the expressway further north to I-84 in Beacon and beyond. This was one of the proposed alignments for I-87. In early 1965, this unconstructed expressway was assigned the designation I-487, allowing a commercial-vehicle-accessible means of travel on the east side of the Hudson River. By 1967, strong resident opposition caused the segment from Peekskill to Beacon to be cancelled. In 1971, the section from Tarrytown to Ossining had also been cancelled due to lack of public support. The only portion that was ever built was the section from Crotonville to Peekskill, and was later named the Croton Expressway. The Croton Expressway opened in 1967 with the US 9 designation. The original surface alignment of US 9 became an extension of NY 9A. Other developments In Albany, US 9 was planned to be upgraded to an expressway. It was to run west from the Dunn Memorial Bridge along the South Mall Arterial (co-signed with US 20), then north along the northern half of the Mid-Crosstown Arterial. The southern half would carry US 9W. The Mid-Crosstown Arterial would have begun at the junction of I-787 and the New York State Thruway, connect with the South Mall Arterial at an underground interchange at Washington Park, and continue north to a junction with I-90. The only portion that was actually constructed was in the vicinity of the I-90 interchange (exit 6). A study by the National Highway Traffic Safety Administration in 2009 found